1. Technical Field
The present invention relates to a print apparatus provided with a function for detecting an end of a print medium.
2. Related Art
With this type of print apparatus, printing is carried out by a print head onto a print medium such as paper that is fed out. With, for example, a serial-type print apparatus, the print head moves in a direction of scanning along with a carriage and ejects ink onto the surface of the printer in the course of this movement, thus printing an image or the like. Provided to a position facing a scanning region of the carriage is a support base that extends along the direction of scanning of the carriage and that projects out in a state where a plurality of ribs (convexities) supporting the paper are spaced in the direction of scanning.
There is also a known print apparatus provided with a function for detecting end positions of the paper or the width of the paper by using a non-contact sensor (for example, an optical sensor) provided to the carriage to sense ends (side ends) of the paper in the direction of scanning by receiving reflected light of light that has been irradiated towards the paper side by the sensor during the scanning of the carriage For example, Japanese laid-open patent publication No. H8-2027 discloses the configuration of a print apparatus provided with a paper width detecting means, wherein a sensor (sensing unit) provided to the carriage irradiates grooves formed on the support base (a guide) with light in order to prevent a malfunction of side end detection of the paper that is caused by when a surface treatment layer of the support base (a guide) is peeled off by abrasion between the support base and the paper and the light reflectance thereof is changed.
However, forming the grooves on the support base causes the paper to be contaminated by ink, paper dust, or the like that has collected in the grooves. Therefore, in a print apparatus of a configuration where the paper is supported with a plurality of ribs, each of the ribs is arranged at a position that essentially does not overlap with the side ends of the paper (which may be, for example, fixed-form paper).
However, the end positions of the paper do sometimes end up overlapping with the positions of the ribs, due to skewing during the feeding of the paper or to positional displacement of the paper in the direction of scanning. Additionally, in the case of paper other than fixed-form paper, the end positions of the paper end up overlapping with the positions of the ribs even though the paper may be fed out correctly. In such cases, when the abrasion with the paper causes considerable loss of the reflection-preventing surface treatment layer applied to the surfaces of the ribs and raises the light reflectance of the ribs, the light reflected from the ribs will result in false detection of the ends of the paper. The fact that abrasion of the ribs is inevitable means that it is necessary to prevent false detection of the end positions in a case where the ends of the paper have overlapped with the positions of the ribs, even when the ribs have been abraded.